Re: Meaning of terms "subexpression" and "constant expression"

Consider the following example:

 #include <iostream>

 template <void (*pf)()>
     struct X
 {
     template <void (*)()>
         struct Y;
     static void instantiate() { (void)m; }

     typedef Y<&X::instantiate> Inst;

     X() { pf(); }
     static X m;
 };

 template <void (*pf)()>
     X<pf> X<pf>::m;

 void f()
 {
     std::cout << "f()\n";
 }

 int main()
 {
     sizeof X<&f>();
 }

According to N3225 - 3.2/2,

An expression is potentially evaluated unless it is an unevaluated
operand (Clause 5) or a subexpression thereof.

Can the expression f in sizeof X<&f>() be considered as subexpression
of X<&f>()? Is the expression f potentially evaluated and is the
function f odr-used?